This invention relates to liquid ring pumps for pumping gases or vapors (hereinafter generically "gas") to compress the gas or to produce a reduced gas pressure region ("vacuum"). More particularly, the invention relates to liquid ring pumps having rotating canisters that are supported by fluid bearing pads.
Liquid ring pumps are well known as shown, for example, by Bissell et al. U.S. Pat. No. 4,498,844. In most such pumps a rotor is rotatably mounted in a stationary annular housing so that the rotor axis is eccentric to the central axis of the housing. The rotor has blades which extend parallel to the rotor axis and which project radially out from that axis so that the blades are equally spaced in the circumferential direction around the rotor. A quantity of a pumping liquid such as water is maintained in the housing. As the rotor rotates, the rotor blades engage the liquid and form it into an annular ring inside the housing. Because the housing is eccentric to the rotor, the liquid ring is also eccentric to the rotor. This means that on one side of the pump--the intake zone--the liquid between adjacent rotor blades is moving radially outward, away from the rotor hub, while on the other side of the pump--the compression zone--the liquid between adjacent rotor blades is moving radially inward toward the rotor hub. A gas intake is connected to the intake zone so that gas to be pumped is pulled into the spaces between adjacent rotor blades where the liquid is moving radially outward. A gas discharge is connected to the compression zone so that gas compressed by the liquid moving radially inward can be discharged from the pump.
A major cause of energy loss in liquid ring pumps is fluid friction between the liquid ring and the stationary housing. Energy loss due to such fluid friction is proportional to the square or an even higher power of the velocity difference between the liquid ring and the housing. To reduce such losses, a substantially cylindrical hollow canister can be provided inside the outer periphery of the pump housing. The housing is stationary, but the canister is free to rotate with the liquid ring. The canister, which is propelled by the fluid drag on its inner surface, tends to rotate at a velocity less than the liquid ring velocity. For example, if the canister velocity is half the liquid ring velocity the fluid friction energy loss between the liquid ring and the canister is one quarter (or less) of the energy loss with no rotating canister.
In order to allow the canister to rotate freely, it must be supported within the housing, for example, by mechanical bearings. As described in Haavik U.S. Pat. No. 5,100,300, the canister can also be supported for rotation by an annular fluid bearing formed by placing a pressurized bearing liquid in the annular clearance between the canister and the stationary housing. In Russian patent 939,826, gas is mixed with the bearing liquid to reduce frictional resistance to rotation of the canister. The frictional drag on the rotating canister can be reduced even more by completely or substantially completely substituting compressed gas for liquid as the rotating canister bearing fluid, as shown in Haavik et al. U.S. Pat. No. 5,370,502.
However, there are several concerns with pumps that use annular fluid bearings to support the rotating canister. One concern is that the thickness of the clearance between the rotating canister and the housing must be fairly small. When compressed gas is used as the bearing fluid, the thickness of the clearance in the radial direction is typically about 0.001 inch. When water is used as the bearing fluid, a typical clearance thickness may be in the range from about 0.002 inch to 0.005 inch. Fairly precise manufacturing techniques must be used to construct pumps with such small clearance thicknesses.
Another concern, especially when liquids are used for the bearing fluid, is that the friction between an annular fluid bearing and the canister may not be as low as it could be. Although this is not as great a concern for rotating canister pumps that use gas for the bearing fluid, any reduction in bearing friction would help to reduce energy loss in the pump.
Further, it would be desirable to be able to provide easily adjustable axial fluid bearings, so that the rotating canister can be confined to a desired axial location.
It is therefore an object of the invention to provide an improved radial fluid bearing for a rotating canister liquid ring pump.
It is another object of the invention to provide an adjustable axial fluid bearing for a rotating canister liquid ring pump.